The present invention relates to an epicycle reduction gear or gear arrangement in which a hydraulic motor is built to be used for a drive device of an endless crawler belt or caterpillar band.
For a conventional epicycle reduction gear having a built-in hydraulic motor, Japanese Patent Laid-open Publication No. SHO 59-147154, Japanese Patent Laid-open Publication No. HEI 11-22789 and Japanese Patent Laid-open Publication No. HEI 4-43 disclose a planetary gear carrier structure of the epicycle reduction gear disposed adjacent to a hydraulic motor housing.
In the structure disclosed in the Japanese Patent Laid-open Publication No. SHO 59-147154, an axial external tooth spline is formed to an outer diameter side of an outer end surface of a hydraulic motor housing, and an axial internal tooth spline formed to an outer diameter side of one side carrier of a carrier carrying both ends of a planetary gear shaft of the epicycle reduction gear is meshed with the outer tooth spline mentioned above. According to such structure, the carrier carrying both ends of the planetary gear shaft is formed independently from the hydraulic motor housing and is integrally secured to the hydraulic motor housing.
On the other hand, in the structure disclosed in the Japanese Patent Laid-open Publication No. HEI 11-22789, a carrier carrying both ends of a planetary gear shaft is independently formed from the hydraulic motor housing and is fastened by means of bolts to an outer end surface of the hydraulic housing case so that the carrier carrying both ends of the planetary gear shaft is integrally secured to the hydraulic motor housing case.
Furthermore, in the structure of the Japanese Patent Laid-open Publication No. HEI 4-43, a support shaft (cantilever shaft) supporting one end of a planetary gear of an epicycle reduction gear is formed to an outer end surface of a hydraulic motor housing case so as to project outward therefrom, and a planetary gear is mounted to this support shaft so that the planetary gear is mounted to the outer end side of the hydraulic motor housing case to be rotatable.
Furthermore, in the epicycle reduction gears or gear arrangements disclosed in the above-mentioned Japanese Patent Laid-open Publication No. SHO 59-147154, Japanese Patent Laid-open Publication No. HEI 11-22789 and Japanese Patent Laid-open Publication No. HEI 4-43, needle bearings rolling around planetary gear shafts are utilized as rotation bearings for the planetary gears.
However, in the structure of mounting the carrier carrying both ends of the planetary gear shaft to the hydraulic motor housing disclosed in the Japanese Patent Laid-open Publication No. SHO 59-147154, the outer diameter of the planetary gear carrier is larger than that of the outer end surface of the hydraulic motor housing case, and hence, an outer diameter of a cylindrical drum rotating on an outer peripheral side of the hydraulic motor housing case is inevitably made large. Accordingly, in a case where such reduction gear mechanism as shown in this Japanese Patent Laid-open Publication No. SHO 59-147154 is utilized as a crawler belt drive device for a vehicle, such as bull-dozer traveling at a fast speed, the rotational peripheral speed of the cylindrical drum will be made fast, which may give an adverse influence on a wearing (abrasion) lifetime of a mechanical seal ring disposed between the cylindrical drum and the hydraulic motor housing case for preventing lubrication oil in the reduction gear from leaking and preventing sediment, soil, small stone, and the like from invading inside. In order to obviate such defect, it has been desired to make reduced an outer diameter of the carrier carrying both ends of the planetary gear shaft to thereby reduce the outer diameter of the cylindrical drum.
Furthermore, in the epicycle reduction gears or gear arrangements disclosed in the Japanese Patent Laid-open Publication No. SHO 59-147154 and Japanese Patent Laid-open Publication No. HEI 11-22789, needle bearings rolling around the planetary gear shafts are utilized as rotation bearings for the planetary gears.
However, in such structures, since a surface pressure is directly loaded to the planetary gear shaft, it becomes necessary to use a planetary gear shaft having a large diameter in the viewpoint of durability and/or strength, which results in an enlargement of the outer diameter of the carrier carrying both ends of the planetary gear shaft. And, it becomes necessary to make high a thrust receiving wall section of the needle bearing, thereby, in cooperation of the enlargement of the diameter of the planetary gear shaft, the outer diameter of the carrier carrying both ends of the planetary gear shaft is made further widened. Because of such reasons mentioned above, the outer diameter of the carrier is made larger than the outer diameter of the hydraulic motor housing case, and hence, the outer diameter of the cylindrical drum rotating on the outer peripheral side of the hydraulic motor housing case becomes inevitably large. It is therefore desired to make reduced the outer diameter of the carrier as well as to improve the planetary gear rotation bearing means with respect to the planetary gear shaft.
Still furthermore, as disclosed in the Japanese Patent Laid-open Publication No. HEI 4-43, in the structure that the planetary gear cantilever support shaft of the epicycle reduction gear is formed, in a projecting manner, to the outer end surface of the hydraulic motor housing case, the planetary gear cantilever support shaft does not exceed the outer diameter of the hydraulic motor housing case, so that the outer diameter of the cylindrical drum rotating on the outer peripheral side of the hydraulic motor housing case can be made smaller. However, this structure provides such a problem as that the cantilever support shaft, which is supported at only one side, may be bent, thus being not practical.
Still furthermore, in the structures of the Japanese Patent Laid-open Publication Nos. SHO 59-147154 and HEI 11-22789, since one side thickened portion of the carrier is overlapped to the hydraulic motor housing case, the axial dimensions of the epicycle reduction gear is made long, and in a case where a crawler belt having a narrow width is utilized, there may cause a case that the end edge of the planetary reduction gear extends beyond over the width of the crawler belt and not disposed within this width, so that there is a fear of damaging the epicycle reduction gear having a built-in hydraulic motor, thus providing a problem, which has been desired to be solved by reducing the axial dimension of the epicycle reduction gear or gear arrangement.
An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide an epicycle reduction gear having a built-in hydraulic motor in which a carrier carrying both ends of a planetary gear shaft is monolithically formed to an outer end surface side of the hydraulic motor housing, reducing an outer diameter of the carrier to be less than an inner diameter of a rotation (rotating) bearing of a rotation (rotating) drum.
This and other object can be achieved according to the present invention by providing an epicycle reduction gear having a built-in hydraulic motor in which a rotation drum formed with internal teeth is rotatably attached to an outer peripheral side of a hydraulic motor housing in which a hydraulic motor is housed and a planetary gear is arranged between an output shaft of the hydraulic motor projecting and extending from the hydraulic motor housing and the internal teeth of the rotation drum to thereby rotate the rotation drum in a speed reduced manner,
wherein the hydraulic motor housing is provided with a shell portion to which the rotation drum is fitted through a rotation bearing and a carrier member carrying both ends of a planetary gear shaft and having an outer diameter less than an inner diameter of the rotation bearing is formed monolithically to an outer end surface portion of the hydraulic motor housing.
According to this structure of this aspect, since the carrier member carrying both ends of a planetary gear shaft is formed monolithically to an outer end surface portion of the hydraulic motor housing, it is not necessary to provide a coupling mount portion which is needed in a structure that a carrier member carrying both ends of the planetary gear shaft is overlapped and coupled to the outer diameter side of the outer end surface portion of the hydraulic motor housing which is formed independently from the carrier member, thus reducing the radial length of the carrier member.
Moreover, a portion of the carrier member on the one side thereof is substituted, in function, with the hydraulic motor housing, so that the axial length of the carrier member is more reduced than one in a structure that a carrier member carrying both ends of the planetary gear shaft is overlapped and coupled to the outer end surface portion of the hydraulic motor housing which is formed independently from the carrier member.
Furthermore, since the carrier member carrying both ends of a planetary gear shaft is formed monolithically to an outer end surface portion of the hydraulic motor housing, the strength of the carrier member against the bending force can be increased and an easy inclination of the planetary gear shaft can be prevented.
Still furthermore, since the outer diameter of the carrier member is made less than the inner diameter of the rotation bearing for the rotation drum which is fitted to the shell portion (outer peripheral portion) of the hydraulic motor, the rotation bearing can be easily and smoothly fitted from the outer end surface side of the hydraulic motor housing.
In a preferred example of this aspect, the carrier member comprises: a plurality of girders formed monolithically to an outer end surface portion of the hydraulic motor housing at substantially equal intervals in a circumferential direction thereof so as to project in an axial direction thereof; an annular carrier wall section monolithically formed to projected front end portions of the girders with a parallel space to the outer end surface portion of the hydraulic motor housing, the annular carrier wall section having an outer diameter less than an outer diameter of the outer end surface portion and being provided, at a radially central portion thereof, with an insertion hole through which the output shaft of the hydraulic motor is inserted; and a planetary gear support shaft portion disposed between the annular carrier wall section and the outer end wall section of the hydraulic motor housing.
According to this structure, the carrier member composed of a plurality of girders and the annular carrier wall section is formed to the outer end surface side of the hydraulic motor housing to be monolithic therewith and the planetary gear support shaft portion is disposed between the outer end wall section of the hydraulic motor housing and the annular carrier wall section so as to support the planetary gear. Therefore, the planetary gear support shaft portion is carried at its both end portions, thus providing a rigid and strong structure of the planetary gear support portion.
In another preferred example, a planetary gear shaft of the planetary gear support shaft portion has one end inserted into a shaft bore formed to the outer end wall section of the hydraulic motor housing and another one end inserted into a shaft bore formed to the annular carrier wall section, a fastening bolt penetrates the interior of the planetary gear shaft in an axial direction thereof and fastens the planetary gear shaft to the outer end wall section of the hydraulic motor housing, and the planetary gear is mounted to the planetary gear shaft through a taper roller bearing to be rotatable.
According to this structure, since the taper roller bearing is used, the planetary gear shaft does not constitutes a roller rolling surface and a surface pressure is not directly applied to the planetary gear shaft. Accordingly, the diameter of the planetary gear shaft can be reduced, and moreover, in the annular carrier wall section having the outer diameter less than the inner diameter of the rotation bearing for the rotation drum, the planetary gear shaft can be supported. Furthermore, since the diameter of the planetary gear shaft is reduced, the planetary gear shaft can be arranged in the space between the outer end wall section of the hydraulic motor housing and the annular carrier wall section, and the outer end wall section of the hydraulic motor housing and the annular carrier wall section can be formed as a position defining wall sections of the taper roller bearing in the axial direction thereof. The planetary gear support shaft portion can be arranged between the outer end wall section of the hydraulic motor housing for fitting the rotation bearing for the rotation drum and the carrier member having the outer diameter less than the inner diameter of the rotation bearing.
In a more structural arrangement, the above object may be achieved by providing an epicycle reduction gear comprising:
a hydraulic motor housing in which a hydraulic motor is housed;
a rotation drum fixed to an outer peripheral side of the hydraulic motor housing through a rotation bearing to be rotatable;
a planetary gear disposed between internal teeth of the rotation drum and an output shaft of the hydraulic motor and supported by a planetary gear support shaft portion; and
a carrier member carrying both ends of the planetary gear shaft, including the planetary gear support shaft portion, having an outer diameter less than an inner diameter of the rotation bearing and being formed monolithically to an outer end surface portion of the hydraulic motor housing.
According to this aspect, substantially the same functions and effects as mentioned above will be achieved.
Further, it is to be noted that the nature and further characteristic features of the present invention will be made more clear from the following descriptions made with reference to the accompanying drawings.